Inverse-phase composite zone plate providing deeper focus than the normal diffraction-limited depth of X-ray microbeams
Inverse-phase composite zone plate providing deeper focus than the normal diffraction-limited depth of X-ray microbeams
复制标题
反相复合波带片提供比 X 射线微束的正常衍射极限深度更深的焦点
DOI：
10.1107/s1600577518016703
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发表时间：
2019
影响因子：
2.5
通讯作者：
Takayama Yuki
中科院分区：
文献类型：
--
作者：
Kagoshima Yasushi;Takayama Yuki
提出了一种新型的波带片（ZP），称为反相复合ZP，以获得比标准衍射极限焦深更深的焦点，而空间分辨率几乎没有降低。该结构是作为常规相位ZP的内部ZP和具有与内部ZP相反相位的三阶衍射的外部ZP的组合。二维复振幅分布的焦点附近的计算使用的单色平面波照明，其中一个维度是径向方向和另一个维度是光轴方向的衍射积分的波光学方法。焦深和空间分辨率作为主要的聚焦特性进行了研究。关于焦深的两个特征有希望的情况下，被发现：一个坑强度焦点与最深的焦深，和一个平强度焦点与更深的焦深比通常的ZPs。结果发现，对于10 keV的X射线能量、钽区材料、84 nm的最小制造区宽度和2.645 µm的区厚度，可以预期两倍的焦深，而空间分辨率几乎没有降低。 在8 ~ 12 keV的光子能量范围内，焦深和空间分辨率几乎没有变化。 反相复合ZP在X射线微束应用中实际厚样品的分析中具有很高的潜力。
A novel type of zone plate (ZP), termed an inverse-phase composite ZP, is proposed to gain a deeper focus than the standard diffraction-limited depth of focus, with little reduction in spatial resolution. The structure is a combination of an inner ZP functioning as a conventional phase ZP and an outer ZP functioning with third-order diffraction with opposite phase to the inner ZP. Two-dimensional complex amplitude distributions neighboring the focal point were calculated using a wave-optical approach of diffraction integration with a monochromatic plane-wave illumination, where one dimension is the radial direction and the other dimension is the optical-axis direction. The depth of focus and the spatial resolution were examined as the main focusing properties. Two characteristic promising cases regarding the depth of focus were found: a pit-intensity focus with the deepest depth of focus, and a flat-intensity focus with deeper depth of focus than usual ZPs. It was found that twice the depth of focus could be expected with little reduction in the spatial resolution for 10 keV X-ray energy, tantalum zone material, 84 nm minimum fabrication zone width, and zone thickness of 2.645 µm. It was also found that the depth of focus and the spatial resolution were almost unchanged in the photon energy range from 8 to 12 keV. The inverse-phase composite ZP has high potential for use in analysis of practical thick samples in X-ray microbeam applications.